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8/17/2019 Brown Clinker
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Gerold Gerold Schnedl /Schnedl / Ingo Ingo Leth Leth
CTECCTEC Quality Quality Days Days 2003 2003
Brown clinkerBrown clinker
BrownBrown cementcement
BrownBrown concreteconcrete
8/17/2019 Brown Clinker
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Brown clinker Sötenich
2Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
TheThe problemproblem::BrownBrown concreteconcrete
8/17/2019 Brown Clinker
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Brown clinker Sötenich
3Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
TheThe reasonreason: Brown clinker: Brown clinker
8/17/2019 Brown Clinker
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Brown clinker Sötenich
4Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Situation Sötenich plant:
Brown cored clinker caused brown cement
and brownish concrete surfaces Market focus: pre-cast cement
Colour of cement / concrete important
Cement less competitive
Problems with brown cored clinker is not new
(since years, but increased in 2002)
but does not always appear
Sometimes problems with brown stainings(Fe2+)
Fuels:
Lignite, presently animal meal
Old burner, old grate cooler
Distinguish between:Colour of cementBrown stainings due to Fe2+
8/17/2019 Brown Clinker
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Brown clinker Sötenich
5Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Study: Find levers to get “black cores”and grey cement
Several industrial tests: Not successful
Higher amount of animal meal causes higher amount of Fe2+
Brown clinker cores even without animal meal
September 2002: Start of systematic clinker sampling
Fuels, kiln conditions, clinker chemistry, granulometry Study in CTEC-Lab
Literature study, microscopy, process data, lab burnedclinker granules
2003: Investment in new burner
8/17/2019 Brown Clinker
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Brown clinker Sötenich
6Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Summary of findings
What causes dark / light clinker ? C4AF is the only dark component in clinker
Incorporation of Mg leads to dark C4AF - changes latticeparameters – semi conductive properties leads to darkcolour
This electrical properties can be disturbed by even smallamounts of other ions. e.g. Fe2+ Mn2+ , Ti4+ or Si4+
Incorporation only when C4AF crystallizes: > 1250 °C Colour depending on condition in sinter zone and
pre-cooling condition (crystallisation) in kiln
Literature
8/17/2019 Brown Clinker
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Brown clinker Sötenich
7Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
What bleaches C4AF in brown cores?
Fe2+ seems to be the main reason in Sötenich but:
Fe2+, Mn2+, Ti, Si in clinker cores: no significant differencesdetectable, but:
No Fe2+ in clinker after cooler does not necessarily meanthat no Fe2+ in liquid phase in sinter zone
Fe2+normally re-oxidised after sinter zone
but needs time and oxygen
Fe2+ appears not only due to reducing conditions:
a) reducing atmosphere or flame touching the lining
b) fuel in clinker (too coarse material – solid fuels..)
c) thermal dissociation of Fe3+ in hot sintering zone
8/17/2019 Brown Clinker
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Brown clinker Sötenich
8Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
What bleaches C4AF in brown cores?
Experience of plants:
The core is brown and never the surface Bigger clinker granules have more often brown cores
More often when kiln is operated at full capacity
Hypothesis, resulting from literature study:
Brown clinker cores seems to be caused by an diffusion effect:Balance of crystallisation speed of C4AF and re-oxidation ofFe2+
Cooling speed > 1250 °C (pre-cooling in kiln)
O2 content in atmosphere / flame Porosity of clinker
Liquid phase content
Even when only very few FeO is detectable < 0,04 %) – meaning that
the not incorporated FeO oxidised afterwards
8/17/2019 Brown Clinker
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Brown clinker Sötenich
9Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Confirmation of hypothesisPlant and lab tests
Analysis of plant clinker samples and process data Fuel mix / fuel rates
burner positions
Extensive microscopic investigation in CTEC-Lab Lab burned clinker with Sötenich raw material
Different cooling conditions over and below 1250 °C
Comparison with other raw meals Impact of atmosphere
Impact of Manganese (Sötenich: 0,2 % MnO in clinker)
8/17/2019 Brown Clinker
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Analysis of plant clinker samples
Influence on animal meal on clinker colour
59,00
60,0061,00
62,00
63,00
64,0065,00
66,00
67,00
68,00
0 0,2 0,4 0,6 0,8 1 1,2
tons / hour animal meal
b r i g h t
n e s s L * c l i n k e r m e a l
No significantimpact of animal
meal on colour, buton FeO content
8/17/2019 Brown Clinker
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Analysis of plant clinker samples
Brightness vs fineness
100
150
200
250
300
350
400
58 60 62 64 66 68
Brightness L*
f i n e n e s s k - v a l u e
k-value (fineness)Coarse clinker hasbrighter (browner)
cores
8/17/2019 Brown Clinker
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Analysis of plant clinker samples
Brightness (L*) vs Literweight
1,00
1,10
1,20
1,30
1,40
1,50
1,60
1,70
55,00 60,00 65,00 70,00
Brightness L*
l i t e r w e i g h t
fraction 11,2-16 mm
fraction 4-8 mm
Dense clinkergranules (higherliter weight) havebrighter cores
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Microscopic examination
Fast cooling
Partly reducing conditions No difference between brown and black cores
High amounts of Alkali Aluminate Fast stiffening
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Lab clinker tests
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Different cooling conditions
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Lab tests to check cooling conditions
Check of different cooling rates > 1250 °C in lab furnace
a1 a2 a3 b c
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Comparison of different conditions
CIZ clinkerReference
5 % MgO 1 % MnO 5 % MgO +1 % MnO
Slowcooled
quickcooled
8/17/2019 Brown Clinker
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Results of process data an lab test study:
Brown cores appear, even only very little FeO is
detectable, nevertheless FeO is the cause
Microscopy investigation – confirms lab burning tests
Partly reducing conditions due to coarse fuel (lignite +animal meal) + divergent flame + sometimes thermal
overheating Too rapid cooling: No pre-cooling zone in kiln caused by
burner position
Rather coarse raw mix causes “overheating” High Manganese content might boost the effect
Coarse clinker granules favour brown cores – due tooxygen diffusion barrier into the core
8/17/2019 Brown Clinker
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Brown clinker Sötenich
1Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Recommendations
Shorter flame – shorter sinter zone
With old burner not possible
Convergent flame – not touching the clinker
With old burner not possible
Move burner into the kiln in order to lengthen cooling zone Detrimental to clinker reactivity
Finer fuels
No coal mill in Sötenich
Finer raw mix decrease coarse Quartz content (raw millimprovement)
Increase SO3 in clinker in order to improve burnability and
produce smaller clinker granules (+ increase workability)
8/17/2019 Brown Clinker
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Brown clinker Sötenich
2Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Industrialisation: A new burner for Sötenich
Not only due to brown cores,also to increase waste fuelrate
Start: 21.05.2003
Shorter, convergent flame
Controllable
8/17/2019 Brown Clinker
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Brown clinker Sötenich
2Feb 03G. Schnedl
CENTRE TECHNIQUE EUROPE CENTRALE
Other plant actions
Manual estimation of clinker colour separation Only black clinker for precast cement
Target: Implement automatic colour measurement of presstablets in auto-lab – result triggers separation of clinker
Implement FeO quick test
Separate clinker
Change fuel mix (reduce
animal meal)
Result: No claims in 2003